A Welsh Ambulance Service worker claims just five ambulances covered the whole of Gwent one day last week.
The worker, who wishes to remain anonymous, told the Argus that on Wednesday October 17 only five ambulances out of 14 were covering Gwent - and three of those five were sent to Bristol at various times.
The worker claims the service is not fulfilling its care of duty to the Welsh public or to its crews and is endangering lives on both counts.
The source also claimed the Welsh Ambulance Service is understaffed due to reductions in overtime, meaning that when crew members are sick or on leave, their shifts aren't being covered.
The source said: "Paramedics are always offering to do overtime, but have been told there isn't enough money.
"On top of that, paramedics get just 30 minutes rest in a 12 hour shift. They are meant to have a further 20 minutes but it’s often forfeited.
"Because we aren’t classed as an emergency service, but an essential one, we get far less funding than the police or fire service. Yet we are probably the busiest of the three.
"Rapid response crews are being put at risk when they arrive one or two hours before an ambulance, and family members get irate when the ambulances don’t arrive.
"At the end of the day, in Gwent, we are covering an area which stretches from Rhymney to Chepstow and St Mellons. You need more than five crews covering an area that big."
We are working with staff and unions to review rota The Argus put all the worker’s allegations to the ambulance service.
Sue Jenkins, director of service delivery at the Welsh Ambulance Service, said ambulances are moved around on a daily basis, meaning the number of crews in an area will change depending on activity and demand.
She said: "Crews from the Gwent area frequently convey patients to hospital in Bristol and other areas across the border into England."
She added while they are committed to responding to patients and providing the very best care possible, they do so within the resources available.
"Work is ongoing with staff and unions to review our current rota and rest break policies which have been in place for a number of years and do not reflect the increase in demand.
She said: "Cover for sick and annual leave as well as overtime is provided where the demand needs are greatest."